Need help with a new dog. ~1 year old. Not sure the breed, but looks dutch shepherd, possibly crossed with boxer. Shows fear aggression. Gets scared when people enter the house or he's yelled at. Won't pee or poop outside until he absolutely has to go. Also plays too aggressively with our other dogs and they are starting to show nervousness and fear because they no longer feel safe. Shelter lied and said basically the opposite of all these things.

Does anybody have advice on actions we can take and a rough estimate of what kind of timeline to expect things to improve? The aggression, particularly towards the other dogs, is forcing us to consider returning him (it is a no-kill shelter). I am completely against it, but ultimately the decision is out of my hands if he doesn't start to improve fast. He's already enrolled in training for these issues, but the trainers keep bailing on appointments at the last minute, and anywhere else in the area has a month long wait list.

Any suggestions, or even just pointing someone in my direction who could help would be greatly appreciated.